Arrangement for improving the commutation in direct current machines



Nov. 17, 1936. H GROB 2,060,935

ARRANGEMENT FOR IMPROVING THE COMMUTATION IN DIRECT CURRENT MACHINESFiled Oct. 22, 1935 //7ve/7z0/: Ha a Gm/J QMXPM Patented Nov. 17, 1936UNITED STATES PATENT OFFICE ARRANGEMENT FOR IMPROVING THE COM- DIRECTCURRENT MUTATION CHINES Utrecht, Netherlands Application October 22,1935, Serial No. 46,147 In Germany September 12, 1934 9 Claims.

This invention relates to a device for improving the commutation ofdirect current machines. In order to reduce self-induction which causessparking at the commutators in machines of this type it is known toprovide for greater spacing between the slot walls of the armature andthe slot copper at a certain distance from the base of the slot at allpoints except at the root of I the tooth.

id In such machines, the distance between the winding wires and the slotwall increases with the distance from the base of the slot to the extentpermitted by the saturation of iron in the outer parts of the teeth.Owing to the increase 5 in the length of the air path of the cross fieldof the slot thus produced, the self-induction of the conductors embeddedin the slots will decrease. Although a construction as described effectsconsiderable reduction of sparking at the commutator, it is still opento certain objections.

One of these objections is that the discharge of the heat developed inthe winding to the surrounding iron is seriously interfered with by theinterposed reinforced insulating layers. Fur- 5 thermore, the armatureconductors with their high specific gravity act upon the center of theslot wedge and subject it to bending stresses, which makes it necessaryto use relatively strong slot wedges and to increase the length of the30 slots accordingly.

The invention eliminates these drawbacks in a simple manner by arrangingthe insulating members disposed, in the known constructions, between theslot copper and the slot walls in the 35 center of the slot whereby theslot winding itself is expanded, so that the copper is separated fromthe iron slot walls only by relatively thin insulating layers. At thisposition of the slot copper the heat developed in the winding is farless 40 prevented from passing over into the closely adjacent iron thanin known constructions and can thus be easily discharged through thesurface of the armature in the normal manner.

A further improvement can be efiected by pro- 45 viding the conductorswith a rectangular instead of a round cross section so as to enlarge theheat eliminating contact surface between the conductors and the wallinsulation considerably.

When the slot copper has the position indi- 50 cated above, the slotwedge is, moreover, not so much subjected to bending stresses as in theknown arrangements.

By way of example, the invention is illustrated in the accompanyingdrawing, in which Figure 55 1 shows a portion of the armature of adirect current machine provided with slots and conductors arrangedtherein; and Figs. 2, 3 and 4 show constructional embodiments similar tothe one disclosed in Fig. 1.

In the slot shape shown in Fig. 1 the space 5 of the slot widenscontinually in upward direction, and the insulating intermediate fillingpart has therefore the form of a wedge. According to Fig. 2, the slot iswidened in steps. The slot shown in Fig. 3 is not widened in its lowerportions, but broadens out towards the top. In the constructionalembodiments shown in Figs. '2 and 3 the intermediate members aretherefore provided only in the upper slot space.

A particularly suitable form of the invention is shown in Fig. 4. Theslot has a gradually expanding cross section, similar to that shown inFig. 2, and the steps are adapted to the electric conductors which maybe of rectangular or square cross section. The slot is lined in theusual manner with an insulating material F which embraces allconductors. The spaces between the conductors B are filled withinsulating members C1, C2, G3 which are introduced between theconductors B after each insertion of a pair of wires, the whole beingheld together by the wedge E in the slot.

The arrangement in which the insulating members fill in the center ofthe slot in a radial direction instead of being disposed adjacent thewalls thereof, particularly if rectangular instead of round conductorsare employed, affords the added advantage that the wire to be insertedlast can in many instances be put in very easily.

If, as in known constructions, the fillers are dis- 5 posed adjacent theslot walls, the first conductor of the top layer which is inserted willbe positioned so as to render it diificult to insert the last conductorwithout considerable shifting of the elements. In the improvedconstruction very little shifting of the elements is required if at all.

This invention is adapted for use with direct current machines having noreversing poles, in other words, machines having no special auxiliarypoles which would otherwise be necessary to obtain satisfactorycommutation. If reversing poles are used they are generally sufficientin themselves to suppress spark formations. While the invention improvescommutation in such machines its advantages are particularly apparentwhere no reversing poles are used since it provides a cheap means toimprove commutation substantially.

If each slot for instance accommodates three instead of two conductorsside by side, the fillers are disposed between every two conductors.

I claim:-

1. An armature having a plurality of slots the side walls of which arespaced apart a greater distance adjacent the open end than at the closedend, a layer of insulating material adjacent said walls and a pluralityof conductors adjacent said insulating material only, said walls beingspaced apart at least at the outer portion a distance greater than thecombined cross section of said conductors and the insulating material,whereby at least a portion of said conductors are centrally spacedapart, and a separate insulating member within said space.

2. An armature as claimed in claim 1, said layer of insulating materialbeing of uniform thickness throughout.

3. An armature as claimed in claim 1, the opposite portions of the sidewalls being parallel and the conductors being arranged in layers, thenumber of said opposite portions being equal to the number of saidconductor layers.

4. An armature as claimed in claim 1, the opposite portions of the wallsbeing parallel, and the conductors being rectangular in cross sectionand arranged in layers equal in number to the number of wall portions.

5. An armature having a plurality of slots the side walls of which arespaced apart a distance greater adjacent the open end than at the closedend, a flange extending circumferentially from each side wall at theperiphery of the armature, an insulating layer adjacent each side wall,a plurality of conductors adjacent each insulating layer and lyingwithin substantially the same radial planes as said flanges and aninsulating member radially disposed between at least the outerconductors whereby the centrifugal force of all of said conductors isopposed by said flanges and the heat from all of said conductors isconducted to said walls.

6. An armature having a plurality of slots the side walls of which arespaced apart a distance greater adjacent the open end than at the closedend, a flange extending in circumferential direction from each side wallat the periphery of the armature, a layer of insulating materialadjacent each of said walls and a plurality of conductors adjacent saidinsulating material and substantially within the same radial planes assaid flanges respectively, said walls being spaced apart at least at theouter portion a distance greater than the combined cross section of saidconductors and the layers of insulating material whereby at least theouter conductors are centrally spaced apart, and a separate insulatingmember within said space.

7. An armature as claimed in claim 6, the opposite portions of the sidewalls being parallel and the conductors being arranged in layers, thenumber of said opposite portions being equal to the number of saidconductor layers.

8. An armature as claimed in claim 6, the opposite portions of the wallsbeing parallel, and the conductors being rectangular in cross sectionandarranged in layers equal in number to the number of wall portions.

9. An arrangement for improving the commutation in direct currentmachines having no reversing poles which comprises, an armature havingplurality of slots the side walls of which are spaced apart a greaterdistance adjacent the open end than at the closed end, a layer ofinsulating material adjacent said walls and a plurality o1 conductorsadjacent said insulating material only. said walls being spaced apart atleast at the outer portion a distance greater than the combined crosssection of the conductors and the insulating material, whereby at leasta portion of said conductors are centrally spaced apart, and a separateinsulating member within said. space.

HUGO GROB.

